1. Field of the Invention
The present invention relates to an apparatus in a book binding machine for producing notches in the back of a book block, wherein the notches extend approximately transversely of the side edges or folded edges of the book block. The book block is mounted in such a way that the book block has a projecting portion. The apparatus includes a cutting tool for producing the notches and an abutment arranged above the cutting tool for laterally supporting the projecting portion of the book block against the cutting force.
2. Description of the Related Art
For improving the stability and durability of a book, prior to gluing the back of the book block, an increase of the sheet edge surface is effected by producing notches extending approximately transversely of the side edges or folded edges. This procedure requires the application of high forces and causes substantial strain on the book binding plant.
When the support of the projecting portion of the book block is unstable, the accuracy to size is insufficient and results in a reduction of the quality of the product being produced.
Because of high frictional forces, stationary lateral support devices for the projecting portion of the book block used in the past resulted in harmful markings, such as scratch marks or undulations. In addition, the support device had to be readjusted or replaced after a certain time because of wear.
As is well known, when cutting the backs of book block by means of so-called circular knives, rotating pressing rollers are used as abutments on both sides of the projecting portion of the book block. Because of the approximately flush cutting plane, these pressing rollers can support the projecting portion of the book block.
However, in producing the notches, the projecting portion of the book block must have a width which corresponds at least to the depth of the notches. When the known pressing rollers are used, the unstable guidance provided by these rollers leads to inaccuracies and damage to the back of the book block.